Mechanical positioning device for precisely determining a series of mechanical locations

ABSTRACT

A movable body member having a series of ratchet teeth is intermittently coupled to a driving force which moves the body member. A ratchet arm is precisely mounted adjacent the series of ratchet teeth to engage the series of teeth when the body member is decoupled from the driving force. A restoring force is applied to the body member to press the ratchet arm firmly against each ratchet tooth with which it comes in contact, thereby precisely locating the body member in a series of mechanical positions. A ratchet spring forces the ratchet arm to engage each tooth of the series of ratchet teeth as each tooth moves adjacent to the arm. A device is provided for restraining the ratchet arm from engaging the ratchet teeth after the last tooth in the series of ratchet teeth is passed. The ratchet arm is restrained until the body member is returned by the restoring force to an initial position where the ratchet arm is released from the restraint and engaged with the ratchet teeth whereby the series of mechanical movements may be repeated.

United States Patent Van Slooten [15] 3,655,020 [451 Apr. 11, 1972MECHANICAL POSITIONING DEVICE FOR PRECISELY DETERMINING A SERIES OFMECHANICAL LOCATIONS Inventor:

11.8. CI. ..l92/142 R, 74/84, 74/116,

Int. Cl ..F16d 71/00, Fl6h 27/04 Field of Search 192/142 R, 143; 74/84,111, 74/116,117, 415, 422, 436

References Cited UNlTED STATES PATENTS French ..74/l16 X PrimaryExaminer-Allan D. Hermann AttorneyPaul R. Harder and Robert J.Steinmeyer [57] ABSTRACT A movable body member having a series ofratchet teeth is intermittently coupled to a driving force which movesthe body member. A ratchet am is precisely mounted adjacent the seriesof ratchet teeth to engage the series of teeth when the body member isdecoupled from the driving force. A restoring force is applied to thebody member to press the ratchet arm firmly against each ratchet toothwith which it comes in contact, thereby precisely locating the bodymember in a series of mechanical positions. A ratchet spring forces theratchet arm to engage each tooth of the series of ratchet teeth as eachtooth moves adjacent to the arm. A device is provided for restrainingthe ratchet arm from engaging the ratchet teeth after the last tooth inthe series of ratchet teeth is passed. The ratchet arm is restraineduntil the body member is returned by the restoring force to an initialposition where the ratchet arm is released from the restraint andengaged with the ratchet teeth whereby the series of mechanicalmovements may be repeated.

9 Claims, 2 Drawing Figures MECHANICAL POSITIONING DEVICE FOR PRECISELYDETERMINING A SERIES OF MECHANICAL LOCATIONS The present inventionrelates to a precision mechanical positioning device and moreparticularly to a mechanical mechanism for precisely locating each of amultiplicity of samples for analysis in a radiant energy analyzer.

In the field of spectrophotometry, it has been the general practice toemploy both manual and automatic methods to insert and remove samplesbeing analyzed.

Although manual methods have served the purpose, they have not provedentirely satisfactory under all conditions of service for the reasonsthat considerable difficulty has been experienced in obtainingqualifiedtechnical personnel, in obtaining more complete data and infreeing experienced personnel from more creative work.

One of the most critical problems confronting designers of automaticspectrophotometers has been the precision positioning of sample cells inthe light beam of the instrument. Slight variations in the mechanicalposition of the sample cell may produce variations in light transmissionwhich significantly effect the instrument indication thereby producingintolerable errors. Prior art mechanisms have utilized large precisioncams or precision gear trains to provide accurate positioning. Thesemechanisms have required a multiplicity of precision elements which hasresulted in undue cost and complexity. These problems have been overcomeby the present invention.

The general purpose of this invention is to provide a precisionpositioning mechanism which embraces all the advantages of similarlyemployed sample cell changing and locating devices and possesses none ofthe aforedescribed disadvantages. To attain this, the present inventioncontemplates a ratchet and ratchet body arrangement in the samplechanging apparatus of a spectrophotometer whereby high cost andcomplexity of precision mechanical elements are avoided.

An object of the present invention is the provision of a mechanicalpositioning device for precisely determining a series of mechanicallocations.

Another object is to provide a ratchet body which engages an accuratelypositioned ratchet arm whereby the ratchet body is precisely located ina series of sequential positions.

A further object of the invention is the provision of a ratchetrestraint to prevent the ratchet from engaging the ratchet body whilethe ratchet body is returned to its initial position after completingits sequence of precision movements.

Still another object is to provide a ratchet body which releases theratchet from the ratchet restraint when the ratchet body has returned toits initial position thereby allowing the ratchet to again engage theratchet body to repeat the sequence of precision movements.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing in which like referencenumerals designate like parts throughout the figures thereof andwherein:

FIG. 1 illustrates a combination of a pictorial view and mechanicalblock diagram of a preferred embodiment of the invention; and,

FIG. 2 illustrates a side elevation of the ratchet body, ratchet arm,ratchet spring, disc drive and microswitch combination as utilized in apreferred embodiment of the invention.

Turning now to FIG. 1, a ratchet body or movable body member 3 isconnected to a mechanical linkage such as rods 4 and 5 which rods areconnected respectively to the ends of body member 3. Rod 4 slidesthrough a sleeve bearing in fixed frame member 6 and rod 5 slidesthrough a sleeve bearing in fixed frame member 8. Rod 5 is furtherconnected to sample tray 10 which slides on a fiat surface of framemember 8. Sample tray 10 is further connected to negator spring 12.

Body member 3 has disposed on a surface thereof a series of ratchetteeth each defining a precise location on the body member. A last tooth14 is essentially larger than the other teeth and a first tooth of theseries has a projecting finger 15. A ratchet arm 16 is pivotally mountedat elbow 17 adjacent to the series of ratchet teeth whereby one end ofthe ratchet arm is aligned to engage a tooth of the series of ratchetteeth as the body member is moved adjacent to the ratchet am. A ratchetspring 18 having detent 20 biases the ratchet arm in a first positionwhereby the ratchet arm is forced to engage each ratchet tooth as thebody member moves with respect to the ratchet arm. When detent 20captures and holds the ratchet arm, the arm is maintained in a secondposition whereby it is restrained from engaging the ratchet teeth onbody member 3.

Body member 3 further has notches 22 disposed along a second surfacewhich are periodically engaged by a protruding finger or driving pin 24connected to rotating disc 26 which in turn is driven by motor 28.Driving pin 24 also intermittently engages a normally closed microswitch30 once every revolution to remove power from the motor thereby stoppingrotating disc 26. Starting switch 32 is connected in parallel withswitch 30.

Operation of the present invention can best be described by reference toFIG. 2. As rotating disc 26 makes one revolution, driving pin 24 engagesone of the notches 22 and moves the body member 3 in the directionindicated by the advance arrow illustrated in FIG. 1. As driving pin 24decouples from one of the notches 22, it engages microswitch 30 andremoves power from the motor to stop the rotation of disc 26. Negatorspring 12 of FIG. 1 supplies a restoring or biasing force which tends tomove the body in the direction indicated by the return arrow and opposethe motion produced by the rotating disc 26 and driving pin 24. Ratchetarm 16 engages a ratchet tooth of body member 3 to prevent the restoringforce from moving the body member 3 in the direction of the return arrowafter the driving pin 24 decouples from one of the notches 22. Ratchetspring 18 applies pressure against ratchet arm 16 to ensure theengagement of the ratchet arm with the ratchet teeth. The restoringforce supplied by negator spring 12 of FIG. 1 forces the tooth engagedby the ratchet arm firmly against the arm to precisely locate bodymember 3. Body member 3 is moved sequentially in the direction of theadvance arrow with the ratchet arm 16 engaging each ratchet tooth ofbody member 3 in sequence and in the manner described above. Eachmovement is initiated by start switch 32 applying power to the motor 28.Switch 32 may be manually operated or programmed automatically toprovide a wide variety of body movement sequences. Although four bodypositions are illustrated in the drawing, it should be clear that anynumber may be obtained by providing an appropriate number of notches andratchet teeth on body member 3.

Body member 3 moves in the direction of the advance arrow illustrated inFIG. 1 until the last tooth 14 which is larger than the other ratchetteeth engages ratchet arm 16 forcing the arm to be captured andrestrained by detent 20 in ratchet spring 18. Since in this restrainedposition ratchet arm 16 cannot engage the ratchet teeth of body member3, there is nothing to prevent the restoring force of negator spring 12of FIG. 1 to move body member 3 in the direction of the return arrowback to its initial starting position. Body member 3 moves rapidly inresponse to the force provided by negator spring 12 until finger 15engages and rotates ratchet arm 16 about elbow 17 in a direction torelease the arm from detent 20 and allow the am again to engage theratchet teeth for repeating the series of mechanical movements of bodymember It should be clear that the preferred embodiment of the presentinvention provides a series of precise mechanical positions whichautomatically and accurately can be obtained on a repetitive basis.Precise positioning is determined by a precisely located ratched armsequentially engaging ratchet teeth precisely located on the body memberto be positioned. A large tooth is provided to end the sequence ofprecision movements by forcing the ratchet arm to be restrained by aratchet spring from further engaging the ratchet teeth. The body memberis returned to its initial position by a restoring force where aprotruding finger releases the ratchet arm from the ratchet spring andallows the ratchet arm again to engage the ratchet teeth to repeat theseries of precision mechanical movements.

Although particular components have been discussed in connection with aspecific embodiment of a radiant energy analyzer having a sample trayprecisely located in accordance with the teachings of the presentinvention, others may be utilized. Furthennore, it will be understoodthat although an exemplary embodiment of the present invention has beendisclosed and discussed, other applications and mechanical arrangementsare possible and that the embodiments disclosed may be subjected tovarious changes, modifications and substitutions without necessarilydeparting from the spirit of the invention.

What is claimed is:

l. A mechanical positioning apparatus for determining a plurality ofprecise mechanical positions comprising:

a movable body member having a series of ratchet teeth thereon, each ofsaid teeth defining a precise mechanical location on said body member;

restoring means for biasing said body member in a first direction;

a ratchet arm precisely mounted adjacent said series of ratchet teeth,said arm having a first position for engaging said teeth to hold saidbody member in a precise mechanical position against the bias of saidrestoring means;

ratchet spring means coupled to said ratchet arm and normally biasingsaid arm in said first position;

drive means intermittently driving said body member in a directionopposite said first direction and against the bias of said restoringmeans, said body member being driven in steps to engage said ratchet armin said first position with at least the next adjacent ratchet toothwhereby said body member is intermittently driven and held in aplurality of precisely defined positions;

means on said body member adjacent the last ratchet tooth of said seriesof teeth for engaging and moving said ratchet arm to a second positionout of engagement with said series of teeth upon the next intermittentmovement of said body member from the position of said body memberdefined by said last ratchet tooth engaged by said ratchet arm;

means holding said ratchet arm in said second position whereby said bodymember is moved in said first direction by said restoring means; and,

means on said body member adjacent the first tooth of said series ofteeth for engaging said ratchet arm and moving said arm from said secondposition to said first position to stop the motion of said body memberin said first direction and to hold said body member until the nextmovement of said body member by said drive means whereby said pluralityof precisely defined positions of said body member may be repeated.

2. The mechanical positioning apparatus defined in claim 1 wherein saiddrive means comprises:

rotating means having a protruding finger, said finger intermittentlyengaging said body member as said rotating means rotates;

an electric motor for driving said rotating means; and,

a switch mounted adjacent to said rotating means for applying power tosaid motor, said switch being engaged by said projecting finger toremove power from said motor at the completion of each revolution ofsaid rotating means.

3. The mechanical positioning apparatus defined in claim 2 wherein saidrestoring means is a mechanical spring.

4. The mechanical positioning apparatus defined in claim 3 furthercomprising a movable tray mechanically attached to said body member,said tray adapted to receive and hold items for precise mechanicalpositioning.

5. In a radiant energy analyzer, a mechanical mechanism for preciselylocating each of a multiplicity of samples in a position for analysis,com rising:

a movable sample ay into which a multiplicity of samples are insertedfor analysis;

a movable body member having a first surface upon which are disposed aseries of ratchet teeth and a second surface upon which are disposed aseries of notches, each of said ratchet teeth defining a precisemechanical location on said body member;

means connecting said sample tray and body member;

restoring means for biasing said body member in a first direction;

a ratchet arm precisely mounted adjacent said series of ratchet teeth,said arm having a first position for engaging said teeth to hold saidbody member in a precise mechanical position against the bias of saidrestoring means;

ratchet spring means coupled to said ratchet arm and normally biasingsaid arm in said first position;

rotating means for intermittently moving said body member in a directionopposite said first direction and against the bias of said restoringmeans, said rotating means having a protruding finger for intermittentlyengaging said series of notches in said body member as said rotatingmeans is rotated whereby said body member is moved in steps to engagesaid ratchet arm in said first position with at least the next adjacentratchet tooth, said ratchet arm holding said body member in one of aplurality of precise mechanical positions when said protruding finger isout of engagement with said series of notches;

means on said body member adjacent the last ratchet tooth of said seriesof teeth for engaging and moving said ratchet arm to a second positionout of engagement with said series of teeth upon the next intermittentmovement of said body member from the position of said body memberdefined by said last ratchet tooth engaged by said ratchet arm;

means for holding said ratchet arm in said second position whereby saidbody member is moved in said first direction by said restoring means;and,

means on said body member adjacent the first tooth of said series ofteeth for engaging said ratchet arm and moving said arm from said secondposition to said first position to stop the motion of said body memberin said first direction and to hold said body member until the nextmovement of said body member by said rotating means whereby saidplurality of precise mechanical positions of said body member connectedto said sample tray may be repeated.

6. The radiant energy analyzer of claim 5 wherein said rotating means isa Geneva movement mechanism comprising a rotating disc having a drivingpin mounted thereon, said driving pin forming said protruding finger;and,

an electric motor connected to said disc for producing rotation.

7. The radiant energy analyzer of claim 6 further including a switch bywhich power is supplied to said motor, said switch being opened by saiddriving pin to remove power from said motor at the end of each completerevolution of said disc.

8. The radiant energy analyzer as described in claim 5 wherein saidrestoring force means comprises a negator spring.

9. The radiant energy analyzer as described in claim 5 wherein saidratchet spring means comprises a leaf spring which normally presses uponthe other end of said ratchet arm and wherein said means for holdingsaid ratchet arm is a detent in said leaf spring, said detent acceptingand holding one end of said ratchet arm when said arm is moved to saidsecond position.

1. A mechanical positioning apparatus for determining a plurality ofprecise mechanical positions comprising: a movable body member having aseries of ratchet teeth thereon, each of said teeth defining a precisemechanical location on said body member; restoring means for biasingsaid body member in a first direction; a ratchet arm precisely mountedadjacent said series of ratchet teeth, said arm having a first positionfor engaging said teeth to hold said body member in a precise mechanicalposition against the bias of said restoring means; ratchet spring meanscoupled to said ratchet arm and normally biasing said arm in said firstposition; drive means intermittently driving said body member in adirection opposite said first direction and against the bias of saidrestoring means, said body member being driven in steps to engage saidratchet arm in said first position with at least the next adjacentratchet tooth whereby said body member is intermittently driven and heldin a plurality of precisely defined positions; means on said body memberadjacent the last ratchet tooth of said series of teeth for engaging andmoving said ratchet arm to a second position out of engagement with saidseries of teeth upon the next intermittent movement of said body memberfrom the position of said body member defined by said last ratchet toothengaged by said ratchet arm; means holding said ratchet arm in saidsecond position whereby said body member is moved in said firstdirection by said restoring means; and, means on said body memberadjacent the first tooth of said series of teeth for engaging saidratchet arm and moving said arm from said second position to said firstposition to stop the motion of said body member in said first directionand to hold said body member until the next movement of said body memberby said drive means whereby said plurality of precisely definedpositions of said body member may be repeated.
 2. The mechanicalpositioning apparatus defined in claim 1 wherein said drive meanscomprises: rotating means having a protruding finger, said fingerintermittently engaging said body member as said rotating means rotates;an electric motor for driving said rotating means; and, a switch mountedadjacent to said rotating means for applying power to said motor, saidswitch being engaged by said projecting finger to remove power from saidmotor at the completion of each revolution of said rotating means. 3.The mechanical positioning apparatus defined in claim 2 wherein saidrestoring means is a mechanical spring.
 4. The mechanical positioningapparatus defined in claim 3 further comprising a movable traymechanically attached to said body member, said tray adapted to receiveand hold items for precise mechanical positioning.
 5. In a radiantenergy analyzer, a mechanical mechanism for precisely locating each of amultiplicity of samples in a position for analysis, comprising: amovable sample tray into which a multiplicity of samples are insertedfor analysis; a movable body member having a first surface upon whichare disposed a series of ratchet teeth and a second surface upon whichare disposed a series of notches, each of said ratchet teeth defining aprecise mechanical location on said body member; means connecting saidsample tray and body member; restoring means for biasing said bodymember in a first direction; a ratchet arm precisely mounted adjacentsaid series of ratchet teeth, said arm having a first position forengaging said teeth to hold said body member in a precise mechanicalposition against the bias of said restoring means; ratchet spring meanscoupled to said ratchet arm and normally biasing said arm in said firstposition; rotating means for intermittently moving said body member in adirection opposite said first direction and against the bias of saidrestoring means, said rotating means having a protruding finger forintermittently engaging said series of notches in said body member assaid rotating means is rotated whereby said body member is moved insteps to engage said ratchet arm in said first position with at leastthe next adjacent ratchet tooth, said ratchet arm holding said bodymember in one of a plurality of precise mechanical positions when saidprotruding finger is out of engagement with said series of notches;means on said body member adjacent the last ratchet tooth of said seriesof teeth for engaging and moving said ratchet arm to a second positionout of engagement with said series of teeth upon the next intermittentmovement of said body member from the position of said body memberdefined by said last ratchet tooth engaged by said ratchet arm; meansfor holding said ratchet arm in said second position whereby said bodymember is moved in said first direction by said restoring means; and,means on said body member adjacent the first tooth of said series ofteeth for engaging said ratchet arm and moving said arm from said secondposition to said first position to stop the motion of said body memberin said first direction and to hold said body member untIl the nextmovement of said body member by said rotating means whereby saidplurality of precise mechanical positions of said body member connectedto said sample tray may be repeated.
 6. The radiant energy analyzer ofclaim 5 wherein said rotating means is a Geneva movement mechanismcomprising a rotating disc having a driving pin mounted thereon, saiddriving pin forming said protruding finger; and, an electric motorconnected to said disc for producing rotation.
 7. The radiant energyanalyzer of claim 6 further including a switch by which power issupplied to said motor, said switch being opened by said driving pin toremove power from said motor at the end of each complete revolution ofsaid disc.
 8. The radiant energy analyzer as described in claim 5wherein said restoring force means comprises a negator spring.
 9. Theradiant energy analyzer as described in claim 5 wherein said ratchetspring means comprises a leaf spring which normally presses upon theother end of said ratchet arm and wherein said means for holding saidratchet arm is a detent in said leaf spring, said detent accepting andholding one end of said ratchet arm when said arm is moved to saidsecond position.